The extrusion process of PVC door and window profile-2

（1） Temperature control

After PVC mixed powder enters the extruder, it should be compacted, transported, melted, homogenized and extruded at a lower temperature. In order to obtain high quality and high output profiles, the temperature of each section needs to be adjusted repeatedly and controlled accurately, so that the materials are always in the melting temperature and decomposition temperature range in the extrusion process. In order to set the temperature correctly, it is necessary to fully consider and guide the relevant factors of material forming temperature.

Factors affecting material processing temperature

1) Formula and raw material quality have the greatest influence on the processing temperature, and the plasticization temperature of the mixture composed of different raw materials is different. After the formula is determined, the processing temperature is basically determined, which only needs to be adjusted in a small range according to the product quality; for the raw materials produced by different manufacturers of the same formula, the extrusion molding temperature is often different, and only through the production practice, according to the quality of the plastic parison, can the setting temperature be adjusted timely.

2) Under normal production conditions, increasing extrusion speed will cause friction and heat generation of materials, so the heating temperature should be properly reduced.

3) If the cooling water is not cold enough, it is easy to cause product deformation. In this case, the extrusion speed can be reduced or the processing temperature can be adjusted according to the product.

4) The heating time before start-up in summer should be shorter than that before start-up in winter. The processing temperature in summer can be slightly lower than that in winter.

5) The display temperature of extruder is the temperature of screw, head and die, not the actual temperature of material. 

When the external heaters of temperature control points such as screw, head and die are heated, the material temperature is actually lower than the display temperature; when the external heaters of temperature control points such as screw, head and die stop heating, the material temperature may be equal to or higher than the display temperature. The corresponding relationship between material temperature, display temperature and set temperature in different extrusion conditions is the basis and benchmark for setting and controlling extrusion temperature.